Modelling of grounding systems for better protection of communication installations against effects from electric power system and lightning

Abstract

This paper addresses three important issues in modelling of grounding systems: modelling of high frequency and transient behavior, of complex and extended grounding systems, and use of software methods. First, modelling of frequency dependent and transient behavior of grounding systems is considered. When simple grounding arrangements are considered then simple steps for improved design for better transient performance may be followed. In cases when they are subjected to fast fronted current impulses, that is, with high frequency content, generation of large peaks of the transient voltages between excitation point and neutral ground during the rise of the current impulse is possible. Described design procedures are aimed at reducing such excessive transient voltages. More complex grounding arrangements may be optimised using suitable computer software. Next, modelling of very complex grounding systems is described. As an example, protection against dangerous voltages between telephone subscriber lines and local ground near high voltage substations due to ground potential rise in case of ground faults is analysed. A computer model of the substation grounding system and connected and near buried metallic structures in an urban environment is used for estimation of the ground potential rise zone of influence on the subscription wire-line installations. Finally, computer software method for analysis of low and high frequency and transient analysis of grounding systems of arbitrary geometry are described.